Serving a life sentence, Mandela suffered through hard labor and petty cruelties. But he transformed isolation into a pulpit for change

Mandela was transferred to Robben Island after his sentencing. In its ignominious past, the flat, windswept rock off Cape Town, battered by the icy waters of the Atlantic, had been a leper colony, a lunatic asylum and a colonial prison where in 1819 the British banished the prophet-warrior commander of the Xhosa rebel army, Makana. Jail was harsh. The guards imposed punishment for even the mildest infractions of regulations. The inmates were made to pound rocks with hammers to create gravel and to mine lime at a quarry. Apartheid persisted even behind bars: black prisoners were given worse food and clothing, their beds were mats on the floor, and they were forced to address the guards as baas, meaning boss. As was intended, serving a sentence on Robben Island meant almost total isolation from the outside world. Mandela went years without seeing his family. When his mother and eldest son died, he was denied permission to attend their funerals. Rigid routine meant the days were endless but also indistinguishable. "The mind begins to turn in on itself," wrote Mandela.

Partly as a survival strategy, Mandela and his comrades resolved to continue their fight inside jail: "I was in a different and smaller arena, [but] the prison was a microcosm of the struggle. We would fight inside as we had fought outside. The racism and repression were the same." Through protests and petitions, Mandela and his comrades gradually improved conditions. In the 1970s, manual labor was stopped. Mandela began a prison garden and wrote a secret memoir, later the basis for his autobiography Long Walk to Freedom. Crucially, while his opposition to apartheid remained fierce, he began to see the humanity in his enemies. "All men, even the most seemingly cold-blooded, have a core of decency," he wrote. "If their hearts are touched, they are capable of changing."

And if Mandela was changing, the outside world was too. On a 1979 trip to a white Cape Town doctor after he injured his heel, Mandela was treated well and thought he sensed a thawing in the relationship between black and white. Mandela was also becoming an international icon for people of all colors. During the Rivonia trial, he had been elected honorary president of the students' union at University College in London; dockworkers around the world threatened not to handle South African goods; and the U.N., members of the U.S. Congress and the leader of the Soviet Union all protested the trial. Mandela became a global symbol of injustice, not least because in 1980 the ANC's leaders in exile decided to explicitly personalize their struggle around him. No longer would they march under banners decrying racism in South Africa. Henceforth their slogan would be simply "Free Mandela." The phrase quickly found its way onto T-shirts and posters around the world and even into a pop song.